Plumb-bob.



A. F. DUGUID.

PLUMB BOB.

APPLICATION m5011111( 28,1913.

1,212,194. Patented 1111.111917'.

ARCHER r. DUGUImorMoN'TREaL, QUEBEC, CANADA. y

PLUlVIB-BOB. i

Specification of Letters Patent. Y

Patentedan. 16, 1917.

Application filed July 28,1913. Serial No. 781,598.

To all tv/wm t may concern:

Be it known that I, ARCHER F. DUGUID, a subject of the King of Great Britain, and resident of the city of Montreal, in the Province of Quebec and Dominion of Canada, have invented certain new and useful Tmprovements in Plumb-Bobs, of which the following is a full, clear, and exact description.

This invention relates to improvements in plumb-bobs for use in connection with various kinds of survey work, but is particularly adaptable for underground work.

The object of the invention is to provide a-plumb-bob by means of which the desired vertical line may be more accurately determined than is at present possible.

The invention is based on the principle that it is much easier to accurately bisect the image of a bright area (symmetrical about its major axis) with the vertical hair of a transit than to set the hair accurately on a plumb-bob string or other d ark object. The means used to put this principle into practice consists of a plumb-bob having slots formed therethrough at various angles, so that however the plumb-bob turns light will always be visible throughat least one of the slots.

In the drawings which illustrate the inventionz-Figure l is a perspective view of the device. Fig. 2 is a vertical sectional view. Fig. 3 is a plan view. Figs. 4 and 5 are partial elevations showing slightly alternative forms.

Referring more particularly to the drawings, 6 designates the cylindrical body of'a plumb-bob which may be either tubular, as

f shown in Figs. l and 2, or solid, as shown in Figs. @L and 5. ln either case, the top and bottom of the body are weighted, the bottom weight being naturally greater. The top 7 is provided vwith an accurately centered aperture 8 for the attachment of a cord 9, while the lower end lO is conically formed, the apex 1l of the cone ,being located exactly in the axis of the body. This axis is designated by the numeral l2. In the form sho-wn in Figs. land 2, the body portion is tubular, as previously stated, and the top 7 and bottom 8 are secured thereto by screw threads or other suitable means, as clearly shown in vFig. 2. A number of diametrically arranged slots 13 are formed through the body one below the other, Y. and in staggered relation;

' Iclaim is symmetricallyarranged on opposite sides of l vertical planes, passing through diameters of the body. lltisV therefore obvious Vthat however the plumb-bob is turned about its axis, the vertical line bisecting the area of light silhoutted by the body'will coincide with the vertical axis of the plumb-bob. It will also be seen that a horizontal line bisecting any of the slots will also coincide with the vertical axis of the plumb-bob. The slots may be rectangular, rhomboidal, elliptical or any other suitable shape. In fact, many of these shapes willV prove more satisfactory in use than the plain rectangles, as it will be much easier to determine the bisecting line. In use, for example, in mines, the plumb-bob is hung in the desired position and an illuminated screen placed behind same. The surveyor then makes hissight and sets his instrument, so that the vertical hair exactly bisects the area of light inclosed by the dark body, as seen in the silhouette.r This operation may be performed much mo-re accurately than would be possible if the stadia hair were sighted on the plumb-bob string. Y

lVhile the device has been shown provided with only four apertures, it is obvious that any suitablenumber may be used and placed at equal angles apart. In outdoor work, the inclosed areas of light would not be so easily visible as in mine work, and in this class of work, it may be found advisable to use a light colored plumb-bob on which dark ribbons are wound. The bob may if necessary be transparent. It is obvious that such minor changes may be made to adapt the device to various classes of work without de- Y parting from the spirit of the invention.

Having thus described l. A cylindrical plumb-bob'having a plurality of diametric slots formed therethrough in staggered relation one to the other, said slots being each symmetrical on opposite sides of a vertical plane Vpassing through a diameter of the bob.

2. A cylindrical plumb-bob having aV vplurality of diametric slots formed theremy invention, what f j Y through, one above the other, said slots being In Witness whereof I have hereunto set my of such size and arrangement thatfthere is hand 1n the presence of two Witnesses.

always a clear View through one of said slots, ARCHER F. DUGUID. the View openingbeing symmetrically ar- Witnesses:

5 ranged on opposite'sides of an imaginary S. RW. ALLEN, line passing ,through the axis of the bob. v G. M. MORELAND.

`G0111 of this patent'n'xy be obtained for ve cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

